As is well known, surgical instruments used in the healthcare industry must be sterilized before and after each use. Sterilization, of course, frees instruments from microorganism contamination, to prevent infections and the spread of diseases among patients. All medical procedures rely upon a stringent program of sterilization.
The medical device industry has addressed the sterilization requirements in the surgical field by offering two general types of surgical instruments: reusable instruments and single use, or disposable, instruments. Reusable instruments are typically composed of stainless steel and are typically sterilized before their initial use and then cleaned and resterilized prior to each subsequent use thereof. Single use or disposable instruments, on the other hand, are often fabricated primarily from plastic materials, thereby reducing costs associated with manufacture, and are discarded after use in a single procedure.
With respect to reusable surgical instruments, e.g., forceps, graspers, dissectors, probes, hemostats, scissors and the like, sterilization and resterilization had historically been accomplished using two primary sterilization modalities: steam sterilization and ethylene oxide sterilization. Of these two primary historical sterilization modalities, steam sterilization had traditionally been the overwhelmingly dominant method of sterilization in the surgical instrument field.
In a broad sense, these historical sterilization processes generally involved placing instruments to be sterilized in a tray, wrapping the instruments and the tray with a sterilization wrap, and placing the wrapped tray and instruments in a sterilization chamber, where the instruments were exposed to the sterilization medium of either steam or ethylene oxide. The instruments were preferably placed in a tray and wrapped before initiating exposure to the sterilization medium. Wrapping the tray generally contributed to providing a level of protection to the surgical instruments, e.g., during post-sterilization storage and handling prior to actual use, and to maintaining the instruments in a dry, sterile condition. Typically, sterilization trays were wrapped with a sterilization wrap, e.g., paper. Other instruments to be sterilized include basins. Basins were separated by cotton towels or other absorbent materials and then wrapped in sterilization wrap prior to sterilization.
One long and continuing problem encountered with steam and ethylene oxide sterilization, however, is the presence of moisture that remains on the implements such as on sterilized instruments, i.e., within the sterile wrap, at the conclusion of the sterilization process. This residual moisture can range from slight levels of dampness to visible droplets on the surface of surgical instruments. Such residual moisture is both undesirable and is unacceptable because such moisture could permit migration of surface microorganisms, thereby penetrating the wrapped tray or basin and rendering its contents contaminated.
A wrapped tray or basin with residual moisture has been termed a “wet pack,” i.e., a wrapped tray containing surgical instruments having surface moisture on the inside and/or outside of the wrapped tray, e.g., during and after the sterilization process. Wet pack problems may be caused and/or exacerbated by, e.g., the use of new sterilizers, boiler or plumbing changes or even ambient humidity variations due to air conditioning, etc.
Another problem associated with steam and ethylene oxide sterilization arises when the wrapped trays and basins are loaded on sterilization carts having multiple shelves and rails and which are then wheeled into a sterilizer where the wrapped trays are sterilized along with the cart. In such a case, condensation may drip from a shelf or a rail onto the wrapped tray causing a wet pack. Also, the wrapped tray or basin may become stained during sterilization or even torn during loading or removal from a sterilization cart because of the condition of the sterilization cart. That is because during repeated use, the sterilization carts may begin to oxidize and degrade, exposing sharp edges.
In some cases, shelves of sterilization carts may be laboriously wrapped with absorbent wrappers or thermal blankets that then must be adhered to the shelves. In a further step, the edges of the absorbent wrappers or thermal blankets must also be bound to prevent fraying and shedding of the wrappers or blankets and subsequent passage thereof into the sterilization medium. Since the absorbent wrappers and thermal blankets require a large amount of labor to replace, the sterilization carts generally undergo an excessively high number of sterilization cycles in the sterilizer before they are replaced. This allows for the buildup of undesirable materials and microorganisms within the absorbent wrappers and thermal blankets.
Many of the disadvantages associated with the two primary sterilization modalities historically used, which are discussed above, are obviated by a third sterilization technique, low temperature hydrogen-peroxide gas plasma sterilization, which is now also being commonly used. For a number of well-known reasons, hydrogen-peroxide gas plasma sterilization is becoming a popular sterilization method. For example, hydrogen-peroxide gas plasma sterilization has significantly less corrosive effect on metal surgical instruments, and leaves no residue that may cause the sterilized surgical instruments to be irritating or toxic to patients. In addition, hydrogen-peroxide gas plasma sterilization produces no toxic byproducts and requires no special ventilation or aeration. Hydrogen-peroxide gas plasma sterilization is also faster than other sterilization processes since a waiting period to allow toxic byproducts to dissipate is unnecessary.
A STERRAD® hydrogen-peroxide gas plasma sterilization system available from Advanced Sterilization Products of Irvine, Calif., for example, is designed to provide non-toxic, dry, low-temperature sterilization in about one hour, without toxic residues. However, the STERRAD® system is not usable with cellulose-based products like linen or paper normally used in other sterilization processes. Cellulose-based products, as well as many other materials commonly used in sterilization, are highly absorbent and trap fluid during the sterilization process. This is highly undesirable in hydrogen-peroxide gas plasma sterilization.
During hydrogen-peroxide gas plasma sterilization, a vacuum is created within the sterilization chamber and a small amount of hydrogen peroxide (e.g., 1 Tbsp) is introduced therein, which, due to the vacuum, vaporizes and substantially fills the chamber. An electrical current is then passed through the chamber in order to convert the vaporized hydrogen peroxide into plasma. As should be obvious to those skilled in the art, any absorbent materials (such as tray liners, pouches, etc.) within the sterilization chamber can trap the hydrogen peroxide vapors, thereby preventing such vapors from filling the chamber and preventing a sufficient amount of plasma from being created.
A similar problem exists with open-cell urethane-based (e.g., polyurethane) foam products, which have been sometimes used in connection with sterilization processes. More specifically, it has been found that the hydrogen peroxide used in connection with hydrogen-peroxide gas plasma sterilization can chemically react with such open-cell urethane-based foam products, such that there is no longer enough vaporized hydrogen peroxide to create sufficient plasma during sterilization.
The STERRAD® system includes a sterilization chamber and a tray for holding surgical instruments and articles such as fiber optic endoscopes, laser handpieces, power drills and ophthalmic devices, within the sterilization chamber during the sterilization process. The tray includes a base having a multiplicity of holes for allowing plasma to flow there through and contact the article being sterilized during the sterilization process.
Existing trayliners and instrument protective pouches for use with the STERRAD® system are known. Examples of such products are available from Cygnus Medical, assignee of the present application, under the trademark Plasma-Cel™. These known trayliners and pouches are formed of an open-cell polyethylene foam, which allows plasma to pass directly through the trayliner or pouch, such that the foam structures do not interfere with the passage of plasma through the tray holes. While these particular open cell foam structures have been found to work effectively with the STERRAD® system, since open cell polyethylene (as well as other open cell foams) is relatively expensive, the structures formed from these materials typically must be reused a number of times to make each individual trayliner or pouch cost effective. Some users, however, feel comfortable with the idea of reusing, and keeping track of the number of uses of, a sterilization trayliner or pouch in a sterile hospital environment. Thus, the relatively expensive open cell polyethylene foam structures are often disposed of after a single use.
U.S. Pat. No. 6,902,712 discloses a highly absorbent liner that may be placed, in one embodiment, as a trayliner in a sterilization tray, e.g., along the tray bottom, or, in another embodiment as a shelf-liner, on a shelf of a sterilization cart, to absorb potential residual moisture generated during the sterilization process. The liner is fabricated from a hydrophilic polyurethane foam.
However, as discussed above, it is undesirable in connection with certain types of sterilization techniques (e.g., hydrogen-peroxide gas plasma sterilization) for absorbent materials to be employed. For example, during hydrogen-peroxide gas plasma sterilization, the highly absorbent material disclosed in U.S. Pat. No. 6,902,712 may cause a significant portion of the hydrogen peroxide to be trapped, such that sufficient amounts of plasma are not created. This problem may be compounded by chemical reaction between the hydrophilic polyurethane foam and the hydrogen peroxide, as described above. Moreover, also as discussed above, the hydrophilic polyurethane foam disclosed in U.S. Pat. No. 6,902,712 is relatively expensive, and the structures formed from these materials typically must be reused a number of times to make each individual trayliner or pouch cost effective.
U.S. Pat. No. 6,391,260 discloses instrument pouches particularly adapted for use in connection with hydrogen-peroxide gas plasma sterilization units. More specifically, an instrument is placed within an instrument pouch in accordance with the invention, and the instrument pouch containing the article is placed within the sterilization chamber of the sterilization unit. The hydrogen-peroxide gas plasma sterilization unit is then operated such that the instrument within the instrument pouch is sterilized, whereby the instrument pouch containing the article is removed from the sterilization unit. The sterilized instrument is left within the instrument pouch until the sterilized instrument is actually used. The instrument pouch is fabricated from a closed cell foam plastic material.
However, while pouches formed from a closed cell foam plastic material may be appropriate for use in connection with hydrogen-peroxide gas plasma sterilization, pouches formed from this material may not provide an adequate level of protection (i.e., cushioning) for the surgical instruments, and may not be cost effective.
What is desired, therefore, is a sterilization accessory which is formed of a material that is capable of being used in conjunction with hydrogen-peroxide gas plasma sterilization, which is formed of a material that does not undesirably trap significant amounts of hydrogen peroxide therein so as to reduce the effectiveness of the sterilization operation, which is formed of a material that does not undesirably chemically react with hydrogen peroxide so as to reduce the effectiveness of the sterilization operation, and which is relatively inexpensive to produce, thereby making it cost effective to dispose of each accessory after a single use.